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Introduction to Dermatology Flashcards

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1
Q

How is the skin formed?

A

Skin arises by juxtaposition of two major embryological elements:
Epidermis - originates from ectoderm
Dermis - arises from mesoderm that comes into contact with inner surface of epidermis

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2
Q

What is the importance of the mesoderm?

A

essential for inducing differentiation of epidermal structures (e.g. hair follicle)

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3
Q

By when is the epidermis formed?

A

Week 4

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4
Q

By when is the periderm formed?

A

Week 5

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5
Q

What is the periderm?

A

Secondary layer of squamous, non-keratinising cuboidal cells

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6
Q

What does the periderm develop?

A

Generates white, waxy protective substance - vernix caseosa

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7
Q

What happens from week 11?

A

basal layer of cuboidal cells ( stratum germinativum) proliferates to form multilayered intermediate zone → four more superficial strata

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8
Q

What are the 4 types of superficial strata?

A

Spinosum(spinous)
granulosum(granular)
lucidum(clear; found on palms of hands and soles of feet)
corneum(horny).

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9
Q

What happens during weeks 9-13?

A

development of hair follicles in stratum germinativum and appearance of lanugo hair

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10
Q

What are melanocytes?

A

derived from neural crest →melanoblasts → migrate dorsally between week 6-8 to developing epidermis (& dermis) and hair folliicles

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11
Q

What happens by week 12-13 to melanocytes?

A

most melanoblasts have reached destination and differentiated into melanocytes

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12
Q

How are melanocytes regulated?

A

Melanocortin 1 receptor (MC1R), a G protein-coupled receptor regulates quantity and quality of melanins produced

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13
Q

What are the three mechanism of regulation?

A

Agonists α-melanocyte-stimulating hormone (αMSH) & adrenocorticotropic hormone (ACTH) → activation of MC1R by agonist → melanogenic cascade → synthesis of eumelanin
Agouti signaling protein (ASP) reverses those effects & elicit production of pheomelanin
ACTH can also up-regulate expression of MC1R gene

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14
Q

When expose to UV how are melanocytes regulated?

A

Increased expression of transcription factor MITF & downstream melanogenic proteins, including Pmel17, MART-1, TYR, TRP1, and DCT → increases in melanin content
Increased PAR2 in keratinocytes → increases uptake & distribution of melanosomes by keratinocytes

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15
Q

Outline the structure of the skin?

A 
Epidermis: 
Basement membrane (dermal-epidermal junction)
Dermis: 
Connective tissue
Subcutaneous fat
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16
Q

What is the epidermis composed of?

A

Keratinocytes

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17
Q

Describe te progressive differentiation of keratinocytes?

A

Progressive differentiation / flattening:
Stratum spinosum
Stratum granulosum
Stratum lucidum (palms and soles only)
Stratum corneum (no nuclei or organelles)

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18
Q

How long does cellular progression from basal layer to the surface take?

A

30 days

Accelerated in skin diseases e.g. psoriasis

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19
Q

What is the role of keratin?

A 
Structural properties
Cell signalling
Stress response
Apoptosis
Wound healing
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20
Q

What are the functions of desmosomes?

A

Major adhesion complex in epidermis
Anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes,
Allow cells to withstand trauma.

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21
Q

What are gap junctions?

A

Clusters of intercellular channels (connexons)
Directly form connections between cytoplasm of adjacent keratinocytes
Essential for cell synchronization, cell differentiation, cell growth and metabolic coordination

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22
Q

What are adheres junctions?

A

Transmembrane structures

Engage with actin skeleton

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23
Q

What are tight junctions?

A

Role in barrier integrity and cell polarity

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24
Q

What is the role of melanocytes?

A

Dendritic

Distribute melanin pigment (in melanosomes) to keratinocytes

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25
What other cells are present in the epidermis?
Melanocytes Langerhans cells Merkel cells Mast cells
26
What is the basement membrane also know as?
dermal-epidermal junction
27
What comprises the basement membrane?
Proteins and glycoproteins | Collagens (IV, VII), laminin, integrins
28
What are the roles of the basement membrane?
Cells adhesion | Cell migration
29
What comprises the dermis?
Papillary dermis | Reticular dermis
30
What is the papillary dermis?
Superficial Loose connective tissue Vascular
31
What is the reticular dermis?
Deep Dense connective tissue Forms bulk of dermis
32
What is the dermis made up of?
Proteins Collagen (80-85% of dermis) – mainly types I and III Elastic fibres (2-4%) – fibrillin, elastin Glycoproteins – fibronectin, fibulin, intregrins – facilitate cell adhesion and cell motility Ground substance – between dermal collagen and elastic tissue – glycosaminoglycan / proteoglycan
33
What cells are present in the dermis?
``` Fibroblasts Histiocytes Mast cells Neutrophils Lymphocytes Dermal dendritic cells ```
34
How is the skin supplied with blood?
– deep and superficial vascular plexus | - does not cross into epidermis
35
How is the skin innervated?
Sensory – free, hair follicles, expanded tips Autonomic Cholinergic – eccrine Adrenergic – eccrine and apocrine
36
What are the two types of afferent nerves in the skin?
Corpuscular | Free
37
What are corpuscular nerves?
Encapsulated receptors | dermis e.g. Pacinian, Meissners
38
What are free nerves?
Non-encapsulated receptors | epidermis e.g. Merkel cell
39
What is the meissner's corpuscle?
Encapsulated, unmyelinated mechanoreceptors Light Touch (+slow vibration) Senses low-frequency stimulation at level of dermal papilla Most concentrated in thick hairless skin, (finger pads and lips)
40
What is the ruffini corpuscle?
``` Slow acting mechanoreceptor Sensitive to skin stretch Deeper in dermis Spindle-shaped Highest density around fingernails Monitors slippage of objects ```
41
What is the pacinian corpuscle?
Encapsulated Rapidly adapting (phasic) mechanoreceptor Deep pressure and vibration (deep touch) Vibrational role - detects surface texture Ovoid Dermal papillae of hands and feet
42
What is a Merkel cell?
Non-encapsulated mechanoreceptors Light / sustained touch, pressure Oval-shaped Modified epidermal cells Stratum basale, directly above basement membrane Most populous in fingertips Also in palms, soles, oral & genital mucosa
43
What is microbiota?
bacteria, fungi and viruses ~ 1 million bacteria /cm2 skin Predominantly Actinobacteria
44
What is the function of the skin?
``` Immunological barrier Physical barrier Thermoregulation Sensation Metabolic functions Aesthetic appearance ```
45
How does the skin act as a physical barrier?
Physical barrier against external environment Subcutaneous fat has important roles in cushioning trauma UV barrier
46
How does the skin act as an immune barrier?
Immune surveillance is also carried out in dermis by: Tissue‐resident T-cells Macrophages Dendritic cells Rapid, effective immunological backup if epidermis breached
47
How does the skin play a role in thermoregulation?
Vasodilatation or vasoconstriction in deep or superficial vascular plexuses → regulate heat loss. Eccrine sweat glands → cooling effect Role in fluid balance
48
What are the metabolic functions of the skin?
Vitamin D synthesis Subcutaneous fat Calorie reserve 80% of total body fat (in non-obese individuals) Hormone (leptin) release - acts on hypothalamus → regulates hunger and energy metabolism
49
Why is aesthetic appearance of the skin important?
Psychosexual | Increased risk of suicide
50
What is the function of the hair?
``` Protection against external factors Sebum Apocrine sweat Thermoregulation Social and sexual interaction Epithelial and melanocyte stem cells ```
51
Where are terminal hairs found?
Scalp, eyebrows and eyelashes
52
Where are vellus hairs found?
Rest of body | hairs (except palms, soles, mucosal regions of lips, and external genitalia)
53
What are the three components of hair cycle?
Anagen Catagen Telogen
54
What happens during anagen?
where new hair forms and grows | 85% of hair; lasts 2-6 years
55
What happens during catagen?
regressing phase | 1% of hair; lasts 3 weeks
56
What happens during telogen?
resting phase 10-15% of hair; lasts 3 months Then loss of old hair
57
Describe the structure of hair?
Hair follicles (pilosebaceous unit) Pockets of epithelium continuous with superficial epidermis Envelop a small papilla of dermis at their base. Arrector pili (smooth muscle) extends at angle between surface of dermis and point in follicle wall. Holocrine sebaceous glands which open into pilary canal → in axillae
58
What is the infundibulum?
Uppermost portion of hair follicle - from opening of sebaceous gland to surface of skin
59
What is the isthmus?
Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
60
What does epithelium keratinisation begin with?
with lack of granular layer named “trichilemmal keratinisation”
61
What is the bulge?
Segment of outer root sheath located at insertion of arrector pili muscle Hair follicle stem cells reside here
62
How can the bulge migrate?
Downward | Upward
63
Describe downward migration?
generate lower anagen hair follicle → enter hair bulb matrix, proliferate and undergo terminal differentiation to form hair shaft and inner root sheath
64
Describe upward migration?
form sebaceous glands and to proliferate in response to wounding
65
What is the bulb?
Lower most portion of hair follicle, includes follicular dermal papilla and hair matrix
66
What is the outer roots sheath?
Extends along from hair bulb to infundibulum and epidermis | Serves as a reservoir of stem cells
67
What is the inner root sheath?
Guides / shapes hair | Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fibre & capillary loop.
68
What is the function of the nails?
Protection of underlying distal phalanx Counterpressure effect to pulp important for walking and tactile sensation Increase dexterity / manipulation of small objects Enhance sensory discrimination Facilitate scratching or grooming
69
Describe the main features of the nail plate?
``` Final product of proliferation and differentiation of nail matrix keratinocytes Emerges from proximal nail fold Grows at 1-3mm/month Firmly attached to nail-bed Detaches at hyponychium Lined laterally by lateral nail folds ```
70
Describe the main features of the nail matrix?
Produces nail plate Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon Lunula only visible proportion Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins Also contains melanocytes
71
What is psoriasis?
Chronic, immune-mediated disorder
72
What are risk factors for psoriasis?
Polygenic predisposition combined with environmental triggers, e.g. trauma, infections, or medications
73
Describe the pathophysiology of psoriasis?
involves T-cells and their interactions with dendritic cells and cells involvement in innate immunity, including keratinocytes
74
What characterises the most common form of psoriasis?
Sharply demarcated, scaly, erythematous plaques
75
What are common sites of involvement ?
are scalp, elbows and knees, followed by nails, hands, feet and trunk (including intergluteal fold)
76
What is the most common systemic manifestation of psoriasis?
Psoriatic arthritis
77
How can psoriasis be managed?
Lifestyle: alcohol and smoking By a dermatologist By a rheumatologist By a psychologist
78
What topical therapies can be used for psoriasis?
Vitamin D analogues Topical corticosteroids Retinoids Topical tacrolimus / pimecrolimus
79
What phototherapy can be used for psoriasis?
Narrowband UVB | PUVA (Psoralen + UVA)
80
What immunosuppressive drugs can be used for psoriasis?
Methotrexate Ciclosporin Fumaric acid esters Apremilast
81
What advanced therapies can be used for psoriasis?
Biologics (anti-TNF, anti-IL17, anti-IL23) | JAK inhibitors
82
What is atopic eczema?
Intensely pruritic chronic inflammatory condition | Complex genetic disease with environmental influences
83
When does eczema typically begin?
During infancy or early childhood
84
What other atopic disorders is it often associated with?
asthma | rhinoconjunctivitis
85
How does eczema present?
Acute inflammation of cheeks, scalp and extensors in infants Flexural inflammation and lichenification in children and adults Fissuring Impetiginisation (Gold crust)
86
How is eczema managed?
Daily emollients and anti-inflammatory therapy Omission of soap Clinical nurse specialist involvement
87
What are the two parts to the pathophysiology of eczema?
Barrier defect | Immune dysregulation
88
Describe the barrier effect
Filaggrin - bind and aggregate keratin bundles and intermediate filaments to form cellular scaffold in corneocytes Reduced extracellular lipids and impaired ceramide production Increased transepidermal water loss (TEWL) Impaired protection against microbes and environmental allergens
89
Describe immune dysregulation
Staphylococcal superantigens stimulate Th2 lymphocyte responses and subvert T‐reg T-cell infiltrate - bias towards Th2 responses Role of microbiome? Eosinophils
90
What topical therapies are used for eczema?
Topical corticosteroids - correct potency for correct site Retinoids (hand dermatitis) Topical tacrolimus / pimecrolimus
91
What phototherapies are used for eczema?
Narrowband UVB | PUVA (hand dermatitis)

Dermatology (4 decks)

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